On 23/07/2021 11:21, Ming Lei wrote:

quoted

Thanks, I was also going to suggest the latter, since it's what
arm_smmu_cmdq_issue_cmdlist() does with IRQs masked that should be most
indicative of where the slowness most likely stems from.

The improvement from 'iommu.strict=0' is very small:

Have you tried turning off the IOMMU to ensure that this is really just 
an IOMMU problem?

You can try setting CONFIG_ARM_SMMU_V3=n in the defconfig or passing 
cmdline param iommu.passthrough=1 to bypass the the SMMU (equivalent to 
disabling for kernel drivers).

Thanks,
John

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